


S4-R4

by Mayonne



Category: Undertale (Video Game), underfell (fandom)
Genre: Alternate Universe - SlaveTale, Alternate Universe - Slavery, Alternate Universe - Underfell, Experimentation, F/M, Happy Ending, Human Souls, Hurt, It Gets Worse Before It Gets Better, Limited Cast of Characters, Pain, Redemption, Short Story, Soul Bond, additional characters are only mentioned, monster magic, monster souls, soul colors
Language: English
Status: Completed
Published: 2016-09-11
Updated: 2016-10-30
Packaged: 2018-08-14 13:37:29
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 8
Words: 15,461
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8016034
Author URL: https://archiveofourown.org/users/Mayonne/pseuds/Mayonne
Summary: <blockquote class="userstuff">
              <p>Monsters are free from the underground. But with that freedom came their hatred against humanity, turning society into servants and slaves as payment for their centuries of captivity. Having just lost her previous master, Sara becomes one more human who's up for grabs. No one, not even her, expected her to become the newest addition to the infamous Doctor W.D. Gaster. </p><p>An Underfell/Slave AU featuring some of the characters from <a href="http://archiveofourown.org/works/6617617/chapters/15142048"> Glass Marble Heart </a></p>
            </blockquote>





	1. Freedom Gained, Freedom Lost

**Author's Note:**

> I had this idea come to me not long after I started working on Glass Marble Heart, but never quite had a clear enough idea of what I'd do with it until now. So, here I am making this little story to fulfill that idea. Hope y'all like it!

It was getting on towards twilight. The sun was more than halfway set behind Mount Ebott, the fading rays filtering through the clouds and trees, casting warm but dusty light. On the other side of the horizon the sky had already begun to don its dark cloak of night and start its chase towards the sun. Life around the base of the mountain was calm, just like any other day for its inhabitants. 

It was a subtle rumble, low and deep to where most did not notice it at all. Others, however, played it off as a trick of the mind if they did. After that there was no warning. The mountain shattered as a massive creature roared, shaking debris from his thick mane and horns before unfurling numerous wings. It looked like a demon from hell as the dust from the broken mountain plumed before it scattered on the wind. Thousands upon thousands of monsters surged behind it like insects scurrying out from a fresh hole with their own cries of victory--and for battle. 

Asgore, the king of all monsters, succeeded in obtaining seven human souls. With all seven absorbed into his being he turned god-like and began his attack upon humanity for unjustly beginning a war against monsters and then sealing them below the mountain with a spell. His rage against humans had burned for ages, affecting the other monsters of his kingdom until all they knew was hate and rage, and looked forward to the day that they would be free and exact revenge. 

It was so quick, so sudden, that humans didn't get much of a chance to launch a counterattack. Those who did try to fight back were massacred unable to withstand the onslaught of nightmarish creatures charging at them nor the magic they held at their disposal. What was body armor to blue-tinted spears that pierced to the soul? Worst of all, it was the monster king himself who led the charge, sweeping away whatever resistance that humans could try to put up.

"You see what has become of us?" Asgore's voice boomed through the air, mixing with the sounds of destruction and screams. "We once cared! We once had compassion! But you showed us no mercy...

"Now expect none from us."

The nation was quickly taken over and monsters began to rule. Any further resistance from humans was met with death, and those who chose not to fight or tried to flee were captured as they were made into servants and slaves for the monsters. Names were lost as they were turned into a combination of letters and numbers stamped onto metal tags for collars around human necks. Families and friends were torn apart as monsters picked and chose which one they wanted like they were nothing more than goods on a shelf. 

Humans saw it as cruelty, monsters saw it as retribution.

• • •

Her lungs and legs burned as she ran, spurred on by panic and the mad hope for freedom. Her mistress, a scrutinizing and critical monster who could either have a normal face or simply a giant eye depending on the number of blinks, had gotten into a scuffle with another monster simply because they wanted the same thing from a particular shop. The tugging on the desired item turned into hissed threats, then yelling, and then a fight, which did not end well for her--now--late mistress. At first she was horrified to see a monster turn to dust, even feeling some of the particles drift onto her skin, but then she realized she was no longer bound and took off. Her attempted escape did not go unnoticed.

One of the guards who regularly patrolled the place, a heavily armored fish or dragon-like monster whose fins stuck out from the helmet in intimidating points, caught onto the sight of her running away and was quickly joined by a Madjick. The guard bellowed orders for her to stop or die, while the other simply giggled in a half-mad amusement as it shot replicas of its orbs through its magic. Some struck at her legs and back, leaving a throbbing ache in their wake, but it was the sure hit to her head that made her stumble and slow her long enough for the guard to reach out and grip at the collar around her neck, making her gag. By instinct her hands went up to try and pull on the opposite end and give herself a chance to catch her breath as she glanced tentatively behind her. 

"Tried scampering off, did you?" the Madjick asked with another little deranged giggle. 

"There's no magic lining her collar," the guard commented as his eyes, hidden in the shadow of his helmet, looked at said object. Usually the collars would have a single, thread-thin line of magic running around the collar like a decorative stripe. That touch of magic served as identification to other monsters who the human belonged to, and also served as a tracking device should the human bound by that magic try to flee from its master. The only way that magic dissolved was either by dusting or the owner willfully transferring ownership to another. 

"Looks like you're up for grabs again. You dust your master, S4-R4?" the guard continued, forcefully spinning her around to face him and looking to the ID code.

S4-R4. The crude reduction of what her name used to be. It had been months since she last heard anyone call her by her name: Sara. 

"No!" she retorted in answer to the question. "A-another monster dusted her. They...they were fighting over something," she added as her body steadily began to tremble in fear of what might happen. 

"She's telling the truth," the other monster chimed. Sara flinched as she caught a dangerous look in the Madjick's eye, peeking out from under its hat, as it looked down at her. "Saw the wretch of her master get dusted before she ran."

"Hmph. All the better." She swallowed hard as the guard's grip tightened around her collar and felt the cold touch of his armor press against her throat, forcing her to draw close until she could feel his breath puffing out from under his helmet. "Don't ever get any ideas. Another stunt like this, and you're dead." The Madjick gave another giddy sound as if hoping it would happen in the next instant. 

Her whole body was trembling at this point. She could see the glint of narrowed eyes boring into her and she nodded her head. "Yes sir," she stuttered, her voice quiet. 

"Good." There was a heavy clanking sound and a yelp from Sara as she was encased in magic that kept her arms pinned to her sides. She didn't try to struggle, she knew already that such an attempt was both useless and humiliating as such displays of magic would not break unless the caster willed it. So, with her shoulders sagging and her head bowed she followed quietly behind the guard.

She was escorted back through the section of the town she had tried to flee from, though it seemed that none of the monsters cared about her passing through. There were, however, the occasional glance from other human slaves who would look in her direction and give a sad look, understand what was to become of her just as any other human who didn't have a current master. She was eventually led to a large apartment complex that used to house people who chose to stay of their own will there, but nearly a year ago when monsters fully took over the country, it had been turned into temporary living quarters and staging area for humans who no longer had masters or had yet to be claimed by one. 

The hallways of the apartments were barren of doors, instead replaced by blue motion-sensing lasers developed by the half mad, lizard-like monster, Doctor Alphys, to keep humans from attempting to break out and escape. The lasers allowed a view into each place, which revealed them all to be size conscious studio apartments. Some of them still held decorations from the previous tenants before monsters forced them out. The magic binding Sara disappeared as they approached one empty apartment, the lasers deactivating for a few moments, before she felt the firm grip of the monster guiding her through at the back of her neck, making her tense and hold her breath. A second later and she was shoved forward to the point that she stumbled and collapsed to all fours within the apartment she'd stay until a new monster came by to peruse the selection. The lasers came back to life with a quiet hum and a faint blue glow, casting an eerie light on either side of the doorway. 

"What do we have here?" questioned a new monster as it skittered along the walls with its dragon-like feet while the rest of its serpentine body slithered about as it moved. The hood of the new monster spread in interest while its tongue flicked in and out of its mouth as it observed the girl through the bars. "A female, hmm? Usually it's the males who find themselves here time and again."

"Previous master was dusted," commented the guard, repeating to the warden what Sara had said to him. 

"What a pity," replied the warden with hardly a drop of sympathy in its voice. "Ah, but you're a new curiosity. I wonder who will become master to this little thing," it continued as it slithered and crawled up and down the walls like a lizard, staring unblinkingly at her. She found herself quickly retreating to the furthest walls of the place. 

"Who knows? I'm heading back out."

The guard who had escorted Sara to the building walked off, the clinking of his armor fading steadily while the warden slithered off as well, likely to continue its patrols up and down the halls and keep track of each human kept in each room. Sara was glad for the privacy and the ease in the air now that she no longer felt she might die or get thrown into the grabbing hands of another harsh master too soon, which allowed her time to look over things in the apartment. Truthfully, there wasn't much. The cupboards in the kitchenette were barren of anything edible, though some of them along with the drawers still held plates, cups, and cutlery. The water still worked as well, but ran only cold water no matter how far Sara put the faucet towards hot. At least the bed still had decent bedding and pillows on it, though even those were in disarray as if someone had been sleeping in them then was dragged out from under the covers. There wasn't much for her to do while stuck there so, for a time, she simply sat on the bed for a while before she found herself lying down and drifting off.

• • •

She would have rested for longer, but being in an unfamiliar room with unfamiliar surroundings kept a part of her mind alert for the slightest change, thus keeping her from sleeping deeply and instead dozing here and there as the hours passed. And it was a good thing too because partway into the night she became aware of movement out in the hall and the sound of voices as they got progressively louder. She had only raised her head to listen in better at first, but when she saw two figures stop outside the doorframe to her particular 'cell.' When she felt eyes on her she reacted quickly and huddled herself into the corner of the bed, since it was pressed to the wall and the headboard created that extra corner for her to curl up into.

"A female?" It was a voice she hadn't heard before. There was the slightest hint of an echo to that masculine sound, giving the figure standing there a more otherworldly feel. 

"Just came in not too long ago," replied another, this time one Sara recognized as the warden to the building. 

"I want to have a look at her."

"Are you certain, sir?" Sara blinked at the hint of respect this new figure was receiving from the warden, when usually monsters showed little of that to any other unless for good reason. Just who was this new person in the building? 

"She'll hardly be useful to what you usually do," the warden continued.

There was a brief moment of silence. Then Sara tensed and pressed her back further against the corner as she heard the sounds of gagging and the faint image of the warden writhing in place. 

"And what would you know of her possible use to me?" the figure asked calmly, yet there was a dangerous undertone to that voice. 

"I wouldn't! I get it!" the warden choked. Immediately afterwards there was a heavy thud as the warden was dropped from where it had been pinned followed by the sound of coughs and gasps as it struggled to regain its breath. 

"Good. Now...let me have a look at her."

Without another question or complaint the lasers barring the doorway were temporarily deactivated and allowed this new figure to stride forward. He was dressed in blacks and grays with the only accent of color being the intense red-purple color similar to a dark wine that glowed from his eyes. With the combination of moonlight and the glow coming from his eyes he looked like some sort of skeleton, even having cracks in his skull which she could only barely make out due to the soft light. 

Once he approached the opposite side of the bed Sara was pressed against he stopped and looked her over with a scrutinizing look she was familiar with due to how her previous mistress was. For a brief instant the lights in his eyes met her own, and she just as quickly brought her gaze away from him.

"How interesting..."

Sara tensed. She knew exactly what he found interesting about her, and it made her dislike her own self again for a moment. She had complete heterochromia; her right eye was a dark brown color like freshly moistened soil from rain, while her left eye was a gray-blue like the skies above as they were beginning to darken with rain. It was that one odd aspect about herself that made her more interesting to monsters and thus made her get snatched up that much faster in comparison to other humans. 

She remained tense as a glow like the one in his eyes manifested itself in the air and formed a phantasmal hand before reaching out and taking hold of her chin with a little more strength than necessary, making her turn her head and keep her eyes on him. But, even then, she tried to keep her gaze off to the side. The rich wine color in his sockets momentarily lit up as he continued to observe her, the effect illuminating the rims of his sockets, which only made him look all the more devilish. Out of the corner of her eye she could see the upward curve of his mouth as he gave a smile that told of unspoken plots.

"Yes, I suppose you'll do."

The phantasmal hand released its grip on her chin and reached further down towards the collar around her neck. When she flinched, attempting to press her back even further against the wall as if hoping she could phase through or disappear, the hand suddenly hooked its fingers over her collar and forced her to lean forward as the monster took another step closer. She wanted to pull back and fight this, but part of her also feared the kind of magic this monster had at his disposal and why the even the warden gave him some sense of respect. So, instead, she whimpered as her trembling limbs got her up to her feet. The tugging on her collar eased to a subtle beckoning with a single finger still hooked around it as she was made to approach until she stood less than arm's length away from this figure who was now to make himself her new master.

The phantom hand that had brought her to him faded away and was replaced by his own hand as he took her collar between his long, slender phalanges. Being so close she now noticed how he bore empty holes in what would otherwise be solid palms. 

Sara's eyes widened at the sight of them as realization finally dawned on her. The cracks in his skull...the holes in his palms... She stood before the infamous Dr. Gaster. He was even more known for his work than even the half-mad Dr. Alphys. He was one of the most prominent monsters within their society, and had near one hundred humans under his control. 

There was a sudden flare of wine colored magic and that same color made a full circle around Sara's neck as her collar was lined with his magic, tagging her as his. Her expression fell as she watched the glow and quietly resigned herself to his will.


	2. His Intent

When Sara was escorted out of the room she saw the warden of the building clinging to the wall with its tongue flicking in and out as it watched her walk away with Dr. Gaster with unblinking eyes. Despite herself she squeaked at seeing the monster there and shied away, stepping closer to the skeleton monster. She then feared she was too close to him and slowed her steps again until he was a full stride ahead of her. He either didn't notice or didn't care. 

She followed him quietly out of the apartment complex, keeping herself a few steps behind him partly because she didn't know what to expect from him and also because she was simply used to walking behind like a shadow. It had been put into her head by her previous mistress: never stand close because then her mistress would be associated with weakness; never speak unless she was addressed by the code on her collar by other monsters, or as 'human' or some other term by her own master; and, whenever addressed to give simple, quiet replies because just as monsters had been silenced by their time underground so were humans now made to keep silent. 

"Human," Dr. Gaster said evenly, having stopped at the outermost area of the complex. Sara came to a sudden halt and looked up at him. "Close your eyes and keep very still. As my newest subject, I have plans for you, and I would prefer to see you make it to the lab in one piece."

Though curiosity began to rise in her in her wondering what he was possibly going to do with her, she just as quickly shoved it back down and nodded her head despite his back being to her and thus his not seeing the gesture. Even so, she gave a quiet 'yes sir' and did as she was told. And then, suddenly, the feeling of the world around her shifted. She kept her eyes screwed shut and her body from trembling too much as she simply felt _nothing_. The sensation ended as quickly as it came and Sara gasped for breath, not having realized the pressure there in her trying to make sense of what just happened. 

Her curiosity rose again when she finally opened her eyes and looked up to see the two of them standing before an old hospital. The front of the building had been blown apart when the monsters first invaded, but then was rebuilt after Dr. Gaster took it over and chose to make use of it for his experiments. He, initially, had other monsters do the work for him before he had collected enough humans to finish the work, who he then kept for said experiments. Sara had heard rumors of how some of his tests were torturous, others even being fatal. A shiver went down the length of her spine as she continued to stare up at the building, unable to stop her imagination from running away from her for a moment as she thought up the possible experiments he would put her through.

She startled when she felt a tug at her collar, the glowing light of the magic lining it intensifying for a moment, making her stumble forward. Dr. Gaster was already striding towards the entrance, his hands tucked behind him, and she quickly got the hint to keep moving so she went into a trot to keep up. 

It was eerie how empty and quiet the front of the building was. If she didn't know any better Sara would have assumed that the place was still deserted. But, the lights were on, the air conditioning still breathed through the vents, and she could see, in the corner of her eye, the movement of monsters as they made use of the skywalks connecting the different wings together as she glanced through the windows. When Dr. Gaster led her to an elevator she hesitated momentarily before she quickly stepped through, keeping her back pressed to the corner and her head down. The ride up to whichever floor he chose felt agonizingly slow, as if time purposefully slowed down so as to force her to stay in his presence for even longer, and it didn't help that she could feel his gaze on her nearly the entire time. It made her feel like a specimen being observed under a microscope. 

Finally the elevator dinged and the doors opposite from where they came in slid open, revealing a long corridor. Sara continued to follow quietly behind the doctor, which gave her the opportunity to try and understand which part of the building she now found herself. Plaques and signs were still on the walls, directing from one area to the next, though some of the information seemed to have been purposefully worn down or removed. In its place were scratches like claws trying to manually replace information or a heavy stamp that still had the faint glow of a monster's magic to make it. The typical doors with their knobs or handles had been replaced as well. Each doorframe now had an automatic sliding door with claw-like machinery on the opposite side giving the clear impression they were there to keep the door sealed. Some windows looking into the patient rooms were cracked but not so much where it could be easily shattered. There was also a haze on every pane of glass, obscuring the full detail of what was inside, though Sara figured there were other humans on the other side. 

And then there were the sounds... She heard moans, groans, and whimpers of people now and then as they passed by certain rooms. And, echoing softly off the walls, distant from their origin, were pained wails and screams, and it made her fear for her safety again as her mind came up with ideas of what happened to them to make them react that way. She had to stop herself from thinking too much since she could already feel her heart rate increase as a mild sense of panic rose within her. 

Gaster had been quietly observing her as they walked the halls. He noticed the small changes in her body language and expression as he continued to lead her towards the room she would stay in. Because of that he couldn't help but pause for a moment and turn around to face her. But, due to her having not paid much attention to him because of her focus on what was going around her, she nearly walked into him. She did, however, catch herself at the last moment with a gasp as she startled. She was already small compared to him, but as she stood before him he noticed how she tried to make herself look even smaller and found a sense of amusement in her timidity. 

"Is there something you wish to say, human?" he asked, smirking.

Her mismatched eyes glanced back and forth between his face and the floor multiple times, unable to keep her focus up on him for anything longer than a second. "What did you do to them?" she whispered.

He let out a low, dark chuckle at her question. He reached out a single hand towards her and he watched her flinch as it drew near, then felt her tense at his touch as he made her tip her head up to look directly at him with his fingertips resting below her chin. "What I did to them satisfies my curiosities. I learn, little by little, what made you humans so capable before, and what has made you so pathetic now. What I do to them best suits my purpose for them, as it will be for you."

Her eyes widened at his words and her body stiffened further, nearly going rigid. Then, hoping he was done talking to her she looked off to the side and began to pull away. But, he surprised her again as he whipped his fingers around her chin, forcing her to keep looking at him. She whimpered at the force he used to keep her there as he bent down to bring his face close to hers. The wine colored glow of his eyes reflected in her own and added a faint overlay to the color of her skin. 

"There is _nothing_ you can do to stop me," he said in the same low and dark a tone as his chuckle before. The lowest rumbles of his voice sounded like that of a growl. "And when I'm done with you, there will be even less."

"What--"

But his expression became cold and distant as he straightened, eased his grip on her chin, and stroked his fingertips gently along her skin there as he drew his hand away to place it behind himself again. He gave the single command of "come" as he turned around and continued walking, leaving Sara both confused and worried over those last words to her. Part of her wanted to bolt in the other direction, but the idea of escape was as insane as Doctor Gaster possibly was. It didn't help that she wasn't familiar with the layout of the building, nor did she have any idea of where she was beyond the walls of the place anyway. With no other possible options for her she went back to keeping her head down as she followed behind. 

They didn't stop again until Gaster led her to a specific room in the middle of a different corridor. They had taken other turns as he led her along, which only further left Sara unable to navigate around the place on her own. At his presence the door activated, the claw-like locks snapping away and allowing the door to slide smoothly open to reveal a typical patient's room. There was, however, a second bed stuffed into the place, allowing for an additional person to stay in the room rather than the usual one. The other usual things found there were gone, such as the television, and other medical equipment used to see to a patient's health. Instead, there was nothing but bare wall with the remnants of old wires and holes in the wall along with the cabinets and drawers for storage. And though there was the same haze on the far window as she had seen from previous rooms there was enough clarity through it to notice the outlines of trees and hills. Gaster gave Sara a sideling glance and she quickly stepped inside while he remained standing outside the room. 

"This is where you will stay, S4-R4. You are not to leave this room, unless called for by me, or to join the others for meals. You will be escorted by either another human, or one of my aids, but never alone. Is that understood?"

"Yes, sir," Sara whispered with her head bowed. 

With a wave of his hand the door slid closed and the latches replaced themselves, locking Sara inside. There were a few moments of silence as she heard him walk away. Then, all the fear and uncertainty building up since first seeing the monster became too much and she buried her face in her hands as she began to sob. As tears spilled from her eyes, wetting her cheeks and hands, another figure who had been watching approached her and laid a gentle hand on her shoulder. Sara startled, snapping her head to the side to see who else was there. 

It was a young woman Sara had never seen before. Tall and lean with skin the color of hot chocolate. Her coal colored hair twisted in tight curls and was pulled back to make a bushy ponytail, and her equally dark eyes looked down at Sara with both pity and understanding. 

"Who are you?" Sara choked, wiping the tears lingering in her eyes.

"C-H-1-0-3. But, my name is Chloe," the girl replied. 

"Sara."

"It's okay, you know," Chloe said, her expression turning sad. "I cried too."

Sara sniffled as she nodded and allowed herself to be lost to tears again. This time, however, Chloe lent the girl her shoulder as they held each other in a hug. It would be some time before Sara stopped crying.


	3. Marked

Chloe was an invaluable source of comfort for Sara that first night in Doctor Gaster's lab. She had rolled their beds together to create a much larger one for them to share when they finally settled down to go to sleep. The entire time as Sara wept Chloe was either hugging her or gently stroking her fingers through the girl's blonde hair. And as sad as it was knowing that this new friend was trapped like she was it still helped to know that she wouldn't be entirely alone. It made falling asleep a little easier too, even with the new surroundings and the lingering fear of what will happen to her. 

Sara remained close to Chloe the following morning as well. The dozens of humans Doctor Gaster had at his command were on a set schedule for meals, and their group was one of the later ones, allowing them a little extra time in the morning to continue resting before the doctor's aides barged in and barked at them to get up and moving. Chloe kept her voice low, whispering explanation and clarification for everything that was happening and whatever else to expect, which Sara greatly appreciated as they held hands to keep track of each other. 

Breakfast wasn't much: a couple slices of bread, a hardboiled egg, and a cup of water. There wasn't salt, or butter, or cutlery of any sort in the cafeteria where all the other slaves quietly sat themselves down to eat. The only sounds there were those of people eating, or the occasional hushed whisper with wary eyes keeping a lookout for any of Doctor Gaster's aids if they patrolled too close. 

"It's the same thing every morning," Chloe whispered between bites of her egg. "The doctor wants all of us in, at least, decent health. Apparently, he prefers to make us last as long as we can so he can make the most of his experiments."

"What's he been doing to you?" Sara asked, worried yet curious about what he had put her through.

"Testing my physical limits lately. It feels like he's got me running marathons every week."

Sara was about to whisper something back to her, but she and nearly the whole of the cafeteria startled when one of the aids squawked.

"S4-R4!"

Chloe's eyes widened for a moment. "Stand up!" she hissed. Stuffing the last bite of her bread into her mouth Sara quickly rose to her feet, nearly smacking her thighs against the edge of the table in her haste. The monster's eyes met hers and the girl swallowed thickly while it felt like her stomach had suddenly dropped down to the floor. 

"Come with me," the monster said evenly, though with a bit of a glare in its eyes.

Sara wove her way through the tables and the people sitting at them. Some didn't bother to raise their heads, instead choosing to keep their gazes down at their food or into their empty cups of water. Others, however, stared at her as she passed and all their looks made her heartbeat steadily quicken until it felt like she could hardly breathe. She kept her eyes down at the feet of the aide who called her as she tugged at her collar as if fiddling with it would help her to breathe easier. She yelped when the aide swatted her hand away, barely scratching at the skin of her hand, and causing the girl to look at it with scared eyes as she cradled her hand. The aide only continued to glare.

The monster made a heel turn and began to lead her out and away from the cafeteria. She worried what was going to happen to her now and couldn't help but glance over her shoulder to get another look at Chloe. Wherever she was going and whatever was going to happen to her Chloe seemed to know, since she had a sad and understanding look on her face as the doors swung shut and broke their eye contact. 

She wrung her hands and chewed on her lip as she quietly followed behind the aide, not really paying attention to where she was being led since part of her figured it wouldn't really matter. She closed her eyes and tried to block out the sound of other humans crying out or whimpering in pain as she continued to walk, but a part of her still ached terribly for them and wanted nothing more than to go to each one and find a way to comfort them in their suffering. It wasn't right the things he was doing to them to make them sound like that, but what could she do against it? Like he had told her, there was nothing she could do. 

Sara was eventually led to a large room that looked like it once was a conference room for staff, but had since been readjusted to suit Gaster's preferences. The very monster stood with his back to her and the aide as they approached and entered, and even then he made no immediate sound or gesture recognizing their presence. The opposite wall was lined from end to the other with tables and desks, and all of them covered in papers and diagrams. Those same phantasmal hands she had seen before were working along the length of the wall, sorting and stacking piles that had begun to form and clear up some of the clutter. The furthest wall had a case full of various, colorful vials and the way they looked made Sara wonder what was inside. 

"Doctor," the aide said eventually, getting its superior's attention. Although he did not turn to look at either of them his act of pulling away from what he was currently looking at to straighten himself and stand tall was enough of an acknowledgment. "Subject S4-R4 for you, sir."

Finally Gaster turned around. Although his gaze was nowhere near as harsh as the aide's own she still felt herself shrink under it, wilting like a flower. She chose to not keep eye contact, though she glanced up enough times to still see his gestures and movements without having to make herself look him in the face. 

Gaster gave a dismissive wave of his hand. "Dismissed," he said, addressing his aide who nodded and quickly walked out. 

It took only a few graceful strides from his long legs to close the space between them and have him stand less than an arm's length from her. He could see her beginning to tremble before him and a part of him took pleasure in the sight. He reached towards her with a single hand and, like last time, felt her tense at his touch as he placed a single fingertip below her chin to make her tilt her head up and meet his eyes. 

"Go stand with your back to the glass," he said slowly, lowly, his voice nearly growling as he looked down at her. She quickly nodded her head and waited for him to remove his hand before slinking past him and going over to the series of glass panels that made up another wall of the room and allowed vision inside. 

It wasn't until she was approaching the wall there that she realized the odd texture to the glass. There were small circular shapes overlapping each other to create what would seem to be some custom texture to the glass, but there were oddities about it that left Sara wondering. The max height to the circles weren't much higher than the top of her head and the range of them were only within a small space of a single pane of glass. Her heartbeat rose again in uncertainty as she pressed her back to the glass, her hands pinned behind her. 

"Hands on either side of your head," he said with that same slow, low tone. 

She swallowed again, her hands trembling, as she brought them up to hover in the air on either side of her head as he had instructed. Gaster chuckled at how she looked before he took a few more strides towards her, overshadowing her due to his far greater height. There was the hint of a smirk on his face as he bent his head down to look at her more closely while he brought his hands to either side of him and pressed them against Sara's own, pinning her hands between his and the glass behind. 

Even pinned as she was she drew her shoulders up closer to her ears as she cowered under him. She squirmed in her fear to try and break free but he wouldn't budge, thus neither could she. 

"Wh-what are you--"

And then that look came back, the look that made Sara feel like a specimen being observed. A second later there was a flare of his wine colored magic originating from the open holes in his palms. Sara gasped in the first instant when she felt a sharp pricking in her own palm, and then let out a high-pitched wail as the pain fully hit her. 

Her screams echoed through the room, past the glass wall, and partway down the corridor the room was located in. Tears quickly welled in her eyes and spilled down her cheeks as she writhed from the pain searing into her hands. It felt like a knife was piercing clear through to the glass behind her and slowly carving a circle into her palm, the ache and throbbing travelling up into her fingertips and all the way to her shoulders. Desperation in trying to avoid the pain kept her writhing in place, all the while sobbing, pleading for him to stop. But Gaster remained unmovable, watching how she moved in reaction to his magic branding onto her, how her brows tensed and furrowed, how tears continued to be forcefully drawn away from her eyes as she kept them screwed shut.

She didn't know how long it took... A few seconds? A few minutes? But, eventually, the worst of the pain stopped as suddenly as it came and Sara collapsed to the floor, gasping and sobbing while her whole body trembled in the lingering pain and throbbing in her nerves from what he had done to her. Through her misty eyes she noticed how her palms on both sides now bore a circular outline in the same wine color as the doctor's magic, her own hands now mimicking the appearance of his. 

"You are _mine_ , S4-R4," Doctor Gaster said, practically hissing. He stood in front of her, standing straight with his hands tucked behind him once again as if he hadn't done anything to her a moment ago. "As is every human here." 

He brought one hand forward again and the empty space in his palm began to glow with his magic around the furthest rim. The same circle now lining Sara's palms did the same and she cried out in pain again, a few more tears leaking from her eyes, as a force originating in her hands pulled her to her feet. 

"You are mine to control, mine to use as I wish." With his magic now infused into her hands he made her stumble forward to him and gripped at her chin with his other hand, staring down at her while the glow in his eyes intensified and reflected in her tears. "And, starting tomorrow, I will make use of you as I wish. As eager as I am to begin my tests, you are a subject too valuable for me to lose focus. Possible negative effects to the result." 

His grip on her chin eased, his phalanges stroking at her skin as he drew his hand away and returned it to being tucked behind his back. But, he still kept his magic-induced grip on her hands, keeping her standing close to him as he continued to stare down at her. 

"I look forward to tomorrow."


	4. Extraction

Sara didn't try to use her hands again until the evening meal since the pain and throbbing lingered in them for hours, leaving her hesitant to try and move or use them as she would normally. But, even during the evening the ache in her hands remained but not so badly where it hurt whenever she flexed her fingers or touched the circle marking either side of her hands. She shed a few more tears later on when she was reunited with Chloe in their room, who only looked at the mark on her hands with understanding and showed her own pair. Sara had been so distracted and worried for herself that she hadn't really noticed till then.

"Why does he do this to us?" Sara asked, her voice quiet as Chloe helped to further ease some of the ache that lingered by gently stroking her fingers or massaging her forearms. 

"He brands us to control us more directly, moreso than the collars can do," she replied. "Some of us think it gives him a bit of pride, too, seeing us marked similarly to him. It'll be better by tomorrow."

"I don't want tomorrow to come," Sara whimpered. "I'm scared. He said he had plans for me, that he was eager to start whatever he wants to do to me, that I was valuable..."

"I don't know why he would say that," Chloe replied, her voice equally soft. "And I wish I could tell you it's going to be okay, but...whatever it is he has planned, it won't be good. It never is." There was a pause between them as they looked at each other before she spoke up again. "Just be brave."

• • •

When she woke up the following day her hands did, indeed, feel much better, just as Chloe had said. There wasn't even the slightest hint of an ache or stinging sensation as she stretched and flexed her hands, testing them in the wake of the branding. After she woke up she simply stared at the wine colored circles in her hands for a few minutes, recalling the shock and pain of them.

She, Chloe, and the other group of humans they ate with had their usual meal of bread, egg, and water, just as the girl had said, but after that Sara was escorted back to their room while Chloe was sent off in another direction. Sara sat in quietly, somehow finding a bit of solace in the silence of the room. She figured it was because the silence meant no pains or plots to leave her trembling in fear or crying in pain. She didn't know how long she sat there on their combined beds but eventually the door slid open and the same glaring aide from the day before greeted her with a barked command for her to follow. 

She wasn't led in the same direction as what was the way leading to Doctor Gaster's office from yesterday. Instead, she was taken down a different series of hallways. As she glanced to the side she noticed some of the plaques and directional guides still stuck to the wall, like in previous corridors, but these were leading her in the direction of various operation rooms. She shuddered at the thought of why they were coming here and what the doctor had in store for her, especially as she remembered his words of his being eager to begin whatever it was he wanted to do. Her trembling only worsened when the aide opened a door to one of those rooms and urged her inside before it walked away. 

Doctor Gaster was waiting for her inside. There was the hint of a pleased smile on his face when she appeared, shuffling into the room. She met his gaze warily while his focus on her was steady, unwavering. She swallowed and clenched her hands into fists in an attempt to keep her hands from shaking too much to be visible, though considering how observant the doctor was it was likely he had already taken notice. A second later she tensed and hissed through her teeth as she felt a sting circling in her hands. There was a pulling feeling in her hands, guiding her further into the room and towards the doctor until she stood before him.

"Lie down with your hands down on either side of you," he said evenly. 

Sara nodded silently and went to the operating table. Hopping up onto it she did as she was ordered, lying down on her back with her hands pressed down onto the table at her sides. Thankfully there was no bright light shining above her as one would usually find hovering above the table, but still she remained looking upwards towards the ceiling since she didn't want to see what he might do. 

So, when she felt a single fingertip float between her breasts, sliding up till it rested ever so lightly at the center of her chest she couldn't help but gasp and tense. "So obedient. So gentle," she heard him say as he closed the space and leaned over her from one side of the table. Unable to look him in the eyes she turned her head away. The faint stinging sensation returned to her hands and she felt them press hard into the table as if another pair of hands were gripping them to keep them there. The force was so strong that she could barely even make her fingers twitch. 

"Let's see now," Gaster murmured, more likely to himself than to them both, as his open palm hovered over her chest. He twirled his hand, each individual finger curling in towards his palm in a beckoning gesture. 

She didn't understand how, but the movement of his hand created a tugging sensation in her chest similar to the feeling of a rubber band as it was stretched further and further. By instinct she resisted the feeling but it only made the tugging feeling in her chest become near painful, like a hand had reached into her ribcage and was pulling at her sternum. Still, she tried to fight it through the increasing pain until tears welled in the corners of her eyes and she cried out as she finally relented.

A green glow rose from the center of her chest, swirling around itself for a moment before it took shape. Sara panted, still feeling the ache and strain in her chest as her eyes looked down and saw the shape form into a little heart and floated a few inches above her. Upon looking at it she suddenly felt as if she had been completely exposed and the feeling made her squirm.

"As I thought," Doctor Gaster said softly. The lights in his eyes were tight and bright, focused entirely on the heart, while his hand reached out and hovered around the shape, not quite touching it but still getting close enough to make Sara whimper and squirm more. 

"Wh--what...is that..."

"This is your soul," he replied, quickly silencing her. "It is the very essence of who you are. Your thoughts, feelings, virtues and vices, experiences and moments that make up who you are all concentrated into this."

Though she still wasn't sure what it was he wanted to do with her soul, she couldn't help herself but shake her head pleadingly at him. But his eyes were not on her face, only her soul. A smile appeared on his face, a smile that wasn't too different from that of a genuinely mad scientist, as he continued to stare at the green heart with unbridled fascination. And the whole time his hands remained hovering around it, yet not quite touching it, as if there were some kind of sensation radiating from it and he was feeling it. 

"Please...don't..."

Finally his gaze turned to her face and she flinched at how cold it was. "You have no say," he retorted.

With one hand still hovering near her soul the other retreated towards his own chest and drew out a little heart shape like her own. However, unlike hers, it was a dim gray color as well as upside down in its orientation, as if it were a reflection of Sara's own. It hovered a few inches from his chest on its own, though the doctor continued to have his hand lingering below it due to his natural instinct to cradle and be cautious with his own essence. 

Then, when he returned his focus to Sara's soul there was a look nothing short of villainous as he reached out with his other hand towards it. Her soul flickered erratically, like a light bulb struggling to stay lit before it burns out entirely, while her breathing shortened as she panicked. She struggled all the more in her panic to try and put distance between herself and Gaster, but it was no use, even as she continued to whimper 'no' and 'please' over and over again. 

The defined shape of her soul turned fuzzy, as if having gone out of focus, and broke apart into streaks of green light. Those lights swirled and orbited around each other the vague shape of the heart it had been in before. With another beckoning gesture with his hand the green strands of light strayed from her and were directed towards his own. 

Sara's whole body went rigid, her back arched high, and a desperate scream erupted from her. 

It was the worst series of sensations she had ever felt. It felt like claws were tearing at every inch of her skin; it felt like her body was rotting from the inside; it felt like a needle the thickness of her fist was piercing into her chest. It felt like she was dying. Her screams continued, working her throat raw, while her whole body twitched with spasms, and tears rolled freely down the sides of her face. 

All the while, Gaster's sockets widened and the lights within them burned brighter as his overall expression remained as that of unstable glee. The gently floating tendrils drawn from her soul moved about in the air like an aurora's light until the very tip touched the surface of his own soul. The surface rippled and the green of her soul spread in a way like that of watercolor on a soaked page. He gasped and groaned at the feeling for a moment before there was a sudden spike in his energy and well of magic he drew from. Wine colored light from his soul and from the magic coursing through him clashed against the gentle green glow, growing steadily brighter as if attempting to drown out the glow. And then the sound of his own laughter clashed against the high-pitched shrieks that Sara continued to release during the whole process. 

He would have drawn more--drawn longer--from her, but the sensation was becoming too intense for him to maintain control of, and the sound of her screams were irritating him. His finger pinched and yanked on the streak of green light like snapping a stray thread and he quickly returned his soul within himself while the tendril was just as quick to retreat to Sara's own. The light was dimmer than before he started, but that didn't matter much to him. Her soul was still intact and still capable of being extracted from again, which was all he cared about. 

He had to take a moment to stand back, panting, as he felt the energy of her soul swirling within him, enhancing every sensation within him to the point where he was nearly trembling where he stood. A pleased chuckle rose from this throat, unbidden. He could tell that there were going to be high hopes for this particular experiment as well as equally high expectations from now on if that was how the first test went. 

Sara, however, felt numb. She lay worryingly still on the table with her eyes barely open but vacant in their gaze, and though her chest rose and fell quickly they were such small breathes it was almost unnoticeable. All the while her soul remained dim, the steady hovering it had maintained above her chest reducing quickly as it lowered. It looked as though the little heart were drooping in a similar fashion to a plant as it wilted. 

Gaster's hand was still trembling from the surge of power within him as he reached out and made her soul return to where it belonged within her. There was the tiniest of whimpers that escaped her lips when it faded from view, but other than that there was no other change in her condition. 

"Don't think I'll let you die from this," he hissed. "I've only just begun."


	5. Aftereffects

**Notes for the Chapter:**

> I apologize in advance. The latter half of the chapter isn't quite up to the quality I usually write, but I'm getting there. Also, thank you, everyone, for your patience!

Breathing was laborious and her chest felt sore; in fact, her whole body ached worse than she ever remembered. Her vision and mind were fuzzy but, little by little, she was regaining focus. There was the muffled sound of a voice she couldn't quite place belonged to until she regained enough consciousness to recall that it was Chloe.

"Sara! Oh, thank goodness, you finally woke up."

"Finally?" she asked, her voice hoarse and soft. She swallowed hoping that the action would moisten her throat and ease some of the scratchy feeling in it. It did, somewhat. "What happened?"

"Doctor Gaster did some kind of experiment to you. You were unconscious for two days after being brought back."

The memory came back, unbidden, at the word _experiment_. It had been nothing like that to her; rather, had been the worst torture she ever had to experience. Just remembering the event made her chest feel worse and bring a hand up to rest at the center of it as if wanting to make sure that the green light he had drawn out of her was still safely inside. It got hard for her to breathe again.

In fact, her focusing her thoughts and feelings onto the center of her being made her sense something within herself. It made her pause for a moment, her brows furrowing in concentration. 

"I feel funny..."

"You're still recovering, it's okay. Take it easy."

"No, I...I don't know how to describe it. Displaced, maybe?"

Perhaps that was the best word for it. After what Doctor Gaster had done to her, drawing from her soul, she didn't feel any less whole if what he said about it being the essence of who she was was true. But there was this odd feeling, distant and faint, surrounded by emotions that weren't her own. It made her furrow her brows further and clutch at her shirt. She didn't want to sense these feelings around her, she just wanted to feel better, to move on from the pain she had gone through and survive. But the more she tried to push the foreign feelings from her the more they fought to stay, resisting her, being stubborn. 

"What's happening to me?"

• • •

"What's happening to me?" he growled, trembling as he held himself steady by leaning against the edge of the table he stood at.

Ever since he had performed the first extraction from the soul of S4-R4 there was a feeling that slowly embedded itself within him, reaching and spreading across like the roots of a plant into soil. It wasn't necessarily unpleasant, it just was strange, foreign, conflicting with the feelings he was so used to. It was like a gentle but steady flow of water against a flimsy wall of stones, slipping past his aloofness and cruelty, and reaching into the depths of his soul. Why did he feel the desire to seek serenity? To seek reprieve from a pain that he believed should be everywhere in his body and yet felt absent within himself? 

Gaster slammed his fist onto the table, creating cracks on the surface as he roared in frustration. Disregarding the damage he had done he brought his other hand to his chest and drew out his soul. He had been noting the changes within his soul for the first few hours after the extraction, and then spacing the observations further apart after the first day. At first there had been no observable change in his soul, only the greater feeling of power he felt within himself. But, after the first day, something could finally be seen happening. Streaks of that gentle green from her soul became visible, slowly making their way across the width of his soul, creating a near whimsical effect. 

Today the streaks had stretched further across the upside-down heart, further emphasizing the whimsical effect of them. For an instant Gaster thought the effect beautiful. Another instant passed and he realized what he was thinking, quickly shoving his soul back into himself. He collapsed into his chair, burying his face into his hands as it got hard for him to breathe. It was the strangest thing to feel such empathy within himself. He tried to fight it, tried to push it down or out of his mind, but the more he tried the more it resisted. What was worse was that a part of him wanted to welcome the feeling. It felt...familiar. But, it also clashed with the emotions he had known for so long, leaving him confused as to which way he should feel, and that in turn only made him feel more frustrated. 

He needed to focus, to return his mind to the reason why he forced her soul out and drew from it. The irritating _feelings_ aside, Gaster's theory and experiment were already beginning to prove true. After watching his majesty, the king, absorb the seven souls he couldn't help but wonder if such an exponential growth in strength and magic were possible on a more individual level; that is, to gain power equivalent to seven souls by drawing from a single soul in increments. Doing so all at once would only kill the subject, which was counteractive to what he wanted to do. So, he had to be patient. 

The results were what he expected, and more. Just from a single extraction of her soul and he could tell that his base abilities had amplified. He had been able to summon numerous more phantom hands to perform more tasks, nearly filling the room with the sight of them and the red-purple glow they emitted. He had also summoned a single blaster, at first, to get a feel for the power it held. Even just the one was far more capable of destruction. When he tested it out the blaster produced a beam with a wide radius and a long range, searing anything within its direct path with his magic. And even then there was some additional damage done by the blast if something was only nearby. He was quite pleased to find out that he had gained a slight area of effect due to the power of the girl's soul.

But, there was still plenty of power he could yet gain from her. A dark chuckle escaped him as he allowed himself a moment to take it all in.

• • •

It was the strangest thing for her to feel these emotions. She knew they weren't hers, but that didn't stop her from feeling them all the same. They pressed in around her like crowded bodies stuffed into a subway train car, and she had to fight to keep them from overwhelming her from her own emotions. Yet, amidst that crowded feeling there was something else there. It felt distant, alone almost, and Sara felt the urge over and over to push her way through everything else to it so she could understand what it was and why it lingered there. But, whenever she tried to pursue that feeling within herself the other emotions not belonging to her crowded even tighter. It was frustrating.

"You're making a face again," Chloe said, pulling the girl out of her thoughts. 

"Oh, sorry," she replied, her voice quiet. 

There was a moment of silence between them; Chloe kept her dark eyes on Sara, while the girl went back to having a distant expression on her face.

"You've been acting a little differently ever since Doctor Gaster summoned you. What did he do to you?"

Sara's mismatched eyes looked into Chloe's own before she brought her eyes down towards her chest, as if seeing the little light there. "He pulled this green colored thing from my chest. He called it my soul."

The girl immediately went rigid while her expression was a mixture of rage and horror. "He didn't..."

"You know about souls?"

"Only from the others. He's never drawn mine out...yet." The last word lingered in the air with a hint of dread, of possible resignation that it could still happen at any time. "And whenever he did, they usually suffered." She chewed on her lip before adding one more bit of information. "Most died. From what the others have said, your soul is everything you are. It's like, condensing every feeling, thought, and sensation into that little thing. But, you said yours was green?"

"Yeah, the light was green." Her gaze became distant again as she looked past the fear and pain of the memories and focused on the moment when she saw it emerge from her. "It was such a soothing color. It was so pretty." She brought her eyes back up to her friend. "Why do you ask?"

"Everyone else who's talked about it mentioned a different color. I haven't heard of somebody with a green colored soul."

"Huh..." Sara muttered, not really focusing again as her attention was being brought inward once more. For a few moments she closed her eyes, returned to that crowded sensation, and reached out a little further to that lonely emotion she felt beyond everything. She swore that, if it were like a human form, maybe it tried to reach out to her in return.

• • •

Doctor Gaster's movements slowed as his expression pulled together into a mixture of disbelief and confusion. Something was stirring within him, something deep and forgotten. A moment later he realized he was crying.


	6. I Know the Feeling

Doctor Gaster's experiments were becoming less frequent, mostly due to the fact of his becoming inexplicably more volatile in recent days. His aides noticed how it looked like he would be struggling with something, clutching at his chest before roaring and unleashing a frightening concentration of magic. It was only a temporary solution as each outrage helped to return him to his usual self. But, with time, that frustration he so clearly emanated would rise until it was beyond his sense of control and he would lash out again. 

What his aides didn't know about the reason why to his behavior was because of the effect of S4-R4's soul on him. They never saw how the green streaks from her own soul decorated his like those in a glass marble. They never understood how he struggled against the softer, sweeter feelings that seemed to settle within himself, stubbornly rooted despite his rage and hate attempting to remove them. And the worst thing was, in his opinion, he wanted to feel these emotions. He blamed it on his curiosity. 

He was losing his patience with it--with each new build-up, each outburst, and each lull between the two. He didn't want to deal with this anymore, and so the only solution was to summon the girl to him. It was time for another extraction anyway. But a part of him was actually worried. His hesitation came from the thought of possibly feeling more of these emotions within him after extracting from her once more. He couldn't afford to feel concern, he needed to see his experiment through to completion. With a growl he scraped his fingers along the edge of the table, leaving scratches that looked like they were made from claws, and looked to the aides staring at him in nervousness and fear for their souls in his presence. 

"Bring me S4-R4. Now."

• • •

Sara winced while in the middle of drinking her water while seated in the cafeteria with the other slaves of her group. She quickly swallowed, slammed the cup to the table, and panted as she trembled all the while feeling like her chest was constricting. She clutched at her chest and fought to keep herself from being overwhelmed by the feelings of anger, frustration, confusion, and cold resolution.

"Sara! Is it getting worse?" Chloe asked, quick to respond to the girl's reactions. 

"N-no, it's just more intense. It'll go away in a second..."

"You've been saying that for days..."

"I'll be fine. I won't...I can't lose myself to this," Sara replied as she felt confusion rise beyond the other emotions within her. Her breathing slowly eased as that one feeling continued to grow. And within the depths of emotion she felt that lonely feeling stir again. She reached out for it again knowing that it was reaching out for her in return. She was about to make contact with it this time, finally recognize what that lonely feeling was, but her concentration broke as an aide barged through the doors and barked out her identification. The feeling slipped away, returning from where it lingered, and Sara felt her own frustration as she quietly rose to her feet and followed the aide. 

The entire walk through the halls to Doctor Gaster Sara simply knew that he would not be pleased to see her. How she knew she could only describe as a feeling, and it got more intense the closer they came leaving her rubbing at the center of her chest as if to ease a physical discomfort there. 

As she guessed Gaster growled low and dark when his eyes met hers. The aide didn't even wait to be dismissed and quickly excused itself with a fearful expression in its eyes as the doctor approached the girl. All the emotions that weren't her own were so much more intense while in his presence. She began to pant again, gripping at her shirt with both hands and cowering into the wall behind her until he loomed over her. Her own fear for her safety made her want to slide down and curl up into a ball, but her reasoning told her it wouldn't make a difference now. With a snarl Gaster whipped his hand forward, his palm open to grip at her throat. 

His hand never made contact.

Sara's back was pressed into the wall, her whole body trembling, her mismatched eyes watching him. Gaster's snarling expression remained on his face, but his own eyes showed hesitation. And, like Sara, he was trembling. 

She could feel the confusion, the anger, so strongly it hurt.

He could feel the fear, the desperate hope of safety against pain, so strongly he nearly felt the urge to shed tears. 

There was a growl, less intimidating than he had planned it to be, and he brought his fingers closer to her throat. "What have you done to me?"

"I...I've done nothing..."

"Don't lie to me!" he roared, slamming both his hands on the wall behind her, making her flinch. "Cease this...whatever you've done!"

"I've done nothing!" Sara cried out in reply, curling up on herself. 

"Look at me when I speak to you, _slave_ ," Gaster hissed, finally reaching out and clamping his fingers around her throat, forcing her to look up and into his flaring sockets. His grip remained trembling, however, as if his strength would fail him at any moment. 

Her eyes stared straight into his. Moments of silence passed between them until the look of fear began to fade away from her face. In its place was a look of sadness, compassion. "It's you," she started, her own trembling hands finally pulling away from her chest and slowly, hesitantly, reaching up for his face. "You're the confusion, the anger, the hate I felt." 

Gaster's sockets widened and the lights within them tightened to pinpricks. There was a sudden surge of compassion he felt in the center of his being, matching the expression on her face, and he pulled away from her suddenly as if she were the terrifying creature rather than the other way around. 

When he drew away her hands returned to gripping at her shirt. "Why do you hold onto it? All the hate and rage? _It hurts_." 

He didn't know what to do. Was it possible that his extracting from her soul inadvertently created a bond between their souls? The thought horrified him. Yet, deep down inside him, there was a piece that took comfort in it--in the gentleness from her. He clutched at his own chest as that same tiny piece of himself lurched forward, desperate. 

"There's goodness in you, I feel it," she said at the same time as the surging feeling. 

Gaster stumbled back to the opposite wall, still clutching at his chest as he felt tears form at the rims of his sockets and spill down his skull. "Stop...please..." 

He shouldn't be feeling any of this. Kindness, compassion, gentleness, all of it could be exploited. All of it could make him be seen as weak. The Underground hadn't been kind to monsters, nor had the humans who had sealed them away in the first place. The world demanded cruelty and a stony heart; there was no use for this kindness he felt inside himself. But it remained. It reached out for him and felt like soft hands caressing at his bones. Oh, how his soul yearned for more. 

The wine color in his eyes flared as he brought his focus onto Sara again and reached out with his free hand. He made a curling motion with his long phalanges, beckoning. He heard her gasp and whimper as her soul obeyed and appeared in front of her chest, bathing her in soft green light. He kept reaching out to her as if to grasp her soul, but he felt her fear as her eyes flicked back and forth between him and the little heart. He recalled with her the excruciating pain she had endured the first time he drew from her. It was enough to make him fall to his knees and shed more tears. 

Such a gentle soul. She didn't deserve the pain and fear he had put her through, but he had made her suffer it nonetheless. It felt as if weights were placed upon his shoulders all at once, making them sag and causing his form to hunch over. He couldn't hurt her further, else he dare to feel deeper remorse for what he had done. With one hand he hid his face from her eyes as tears brought on by that remorse fell. 

"Get out," he breathed. But she stalled, and even dared to take a step towards him. "Get out!" he roared. 

Startled, Sara took a step back then quickly left the room and ran. She remained clutching at her chest as she shared his tears.


	7. Sara

**Notes for the Chapter:**

> Surprise! Extra chapter for all of you, my lovelies~ 
> 
> We're almost done with this story!

Doctor Gaster remained unable to see to any of his experiments for the rest of the day. Instead, he excused himself to his private quarters, which were a number of rooms in the old hospital he remodeled into an organized--if simplistic--master bedroom and study area. He needed time to sort through the information and emotions that swirled about unorganized like loose paper caught in a wind. 

In his extracting from her soul to empower himself he had bonded with her. It explained the streaks of green that spread across the width of his soul. They hadn't been a sign of just the resilience and enduring power of her soul fusing with his, but of the solidifying bond he had made with her. The feelings that lingered within him, clashing against the ones he was so used to experiencing, were hers and her attempting to reach into the depths of who he was, whether consciously or not. By now her kind soul felt all the stronger within him, rousing the similar emotions he thought he had left behind ages ago. 

He was no longer confused about it all, nor was the frustration nearly as great at this point. In fact, as he sat, he felt sorrow, compassion, and the yearning for happiness until it made him shudder, his bones rattling quietly. 

_It hurts_. Those were the words she had uttered when describing the hate and anger he and all of monster-kind had clung to. She wasn't wrong. Thinking back on all his years of being violent and hostile, raging against himself and others in order to assert himself, the end result left him feeling tired and worn. His forgotten feelings of compassion and kindness reached out beyond all that and he nearly groaned in his yearning to feel it all the more intensely, but it had been so long since he had acknowledged these emotions and they felt as tired and worn as he currently did. 

He felt her then, her gentle soul rising with his forgotten feelings. He could imagine her standing before him with that sad look on her face, but with her arms reaching out to him in the hope that he would accept the invitation of peace she offered. But what right did he have to expect that amount of kindness and understanding from her? He had tortured her, treated the very essence of her as little more than a thing, seen her as little more than an opportunity. But she bore a kind soul, so that's simply how she acted and reacted. He let out a real groan as he hunched over, feeling her more strongly as if she were actually there before him and touching him gently. 

He didn't deserve this...

• • •

Sara couldn't sleep. She felt much too restless, and knew now that it was because of Doctor Gaster. He was troubled and it was seeping over towards her, leaving her feeling just as troubled even though she didn't know what sort of thoughts brought on the emotion. Regardless it stirred her soul, and despite her hesitation due to what he had done to her there was no denying that she felt sorry for him when he himself felt sorry. He wasn't a inherently cruel person. Rather, it had been developed and then maintained while the gentler emotions were pushed aside.

She currently felt two emotions within herself; one was a yearning, desperate in its want to feel more of her kindness, while the other was a hesitation, a denial, of seeking it out. He wanted her nearby but didn't feel like he deserved that. To Sara, however, she felt he deserved to be forgiven and feel peace if he was willing to be forgiven. People were just as capable of cruelty, just as capable of changing for the better, so why wouldn't the same apply to monsters like Gaster? 

Careful not to rouse Chloe from her own slumber Sara rose to a sitting position on the edge of their joined beds and then slipped off entirely. As she approached the locked door it felt as if the doctor was right outside waiting for her. But as much as she wanted to follow the feeling and actually find him there was nothing she could do. She leaned her forehead against the cool metal and closed her eyes as she brought her focus inward and hoped he would feel her plea.

• • •

__

_I'm coming...Let me in..._

The sensation startled him to rising, one hand clutching at his chest while the other gripped tightly on the arm of the chair he had been sitting in. She was trying to come to him? Why? He didn't... He couldn't fight it, didn't want to. Without a word he made a subtle sweeping gesture with his hand.

• • •

Sara tensed and hissed at the stinging sensation in her hand due to the brands there. But the feeling was quickly forgotten as the sensation of Gaster's magic was enough to be registered to the door, and it unlocked and slid open. She was hesitant, at first, as she peeked her head out of the doorway and looked down the hallway. There were no lights to illuminate the length of the hall, leaving only the moonlight to cast a faint glow through the occasional window. The silence was just as eerie as the appearance. Her imagination got away from her for a moment and she thought there to be things in the shadows.

The feeling as if Gaster was nearby remained. It felt as if he were still standing before her, despite his physical presence being elsewhere. Following the feeling she turned into the corridor. Her footfalls echoed quietly as she walked, passing by the other rooms housing the other slaves. Most were quiet, though there were one or two she passed by where she could barely make out the sound of hushed conversation. What they were discussing wasn't important, so she didn't bother to slow down to listen in, and instead kept her gaze forward as the feeling of Gaster grew stronger the further into the building she went. 

She was grateful she never ran into one of the aides. She knew, from the short time she had spent here, along with word of mouth from the others, that they sometimes did nighttime patrols just in case one of the other humans tried to be clever and escape. None ever did, though. Her initial wariness of their lingering around the halls dissipated the further she went until she was trotting along, one hand still clinging to her shirt while, with her other hand, she brushed the walls with her fingertips. 

The feeling, the distinct pulling at the center of her chest, led her a section of the building she had never stepped in before. But, from what she could tell, it wasn't far from the office room she had been brought to the other day when Gaster branded his mark onto her hands. It looked as though whatever luxury material could be spared from the building had been collected and used for this particular area, but it made sense to Sara due to the doctor being the one in charge, thus getting the best pick of everything. She brushed her hand down the dark wood door to the metal knob and tested it. Unlocked. The feeling of him stirred more erratically as she turned the knob, opened the door, and found the monster sitting not too far off in a chair with his head buried in his hands. 

She didn't need to say a word for him to acknowledge her presence. Like she could feel him growing stronger the closer she came to him, the same could be said for Gaster and the sensation of her within himself. However, when he brought his head up to look at her he had a distressed expression on his face.

"No...you shouldn't be here," he murmured. "You shouldn't...I'm not...I..." Gaster couldn't get a full sentence out, unable to figure out what he should say at all, and in the end he buried his head into his hands again. 

"You want me here," Sara gently retorted as she took slow, cautious steps towards him. "You want me to forgive you, I can feel that. You know I'm willing to."

"Yes," he chocked as his hands clenched. "But, after everything I've done... _how_ could you be willing to forgive me? I was harsh, cruel. The pain I've put you through..."

"Pain passes," she replied, drawing ever closer. "Besides, it's not as if humanity is free of that same cruelty. We've been terrible to our own for ages. But, no matter how dark things may seem there will always be someone willing to rise above that. _You're_ trying, that's something."

By the time she finished speaking she was standing in front of him. He startled when he felt her fingertips touch at his hands, and when he brought his head up her touch moved inward to gently touch at his face. Though his expression looked pained there was a wave of relief that washed over him at her touch, which caused the both of them to sigh in tandem. 

"I don't know if I'm strong enough to keep trying. It's been so long since I've felt like this."

"But it'll be worth it, in the end."

Such hope. Such kindness. Gaster's own hands reached out for her. With one hand he gently curled his long, slender fingers around her wrist while with the other he reached out and brushed the tips along the soft curve of her jaw and chin. That same hand paused as his eyes went down and took in the sight of the collar around her neck and its metal showing the four simple symbols making up the identification that his kind had made. He saw her throat move from her swallowing as he reached for it and lightly touched the tips of his phalanges against the engraved metal. He was a brilliant monster, so it didn't take him very long to see what those four symbols were meant to really say. 

"Sara," he whispered, looking up into her eyes. 

She blinked, softly gasping at the sound of her name. But her wonder at his calling her by name was short lived as she blinked in confusion due to his leaning into her and burying his face into her shirt. His hands took firm fistfuls of the fabric, feeling him tug a little bit as if finding some kind of reassurance in feeling her there. 

"Forgive me."

Her expression turned sad, yet compassionate, as she looked down at him. She rested her hands lightly on top of his head and closed her eyes as she brought her focus inward once more. Her softer, sweeter emotions reached out for his own and they freely reached out in return. From the relief that still lingered within him she felt him grow more and more peaceful as well as the effect of her soul on his grew stronger. Neither saw how Sara's chest began to emit a gentle green glow while Gaster's own did the same. The color of her soul radiated gently within the monster's own, seeming to shift and move like an aurora within him. 

"I forgive you," she whispered. 

The feelings of hate, anger, and pain were pacified to the point where it felt like they hadn't been a part of Gaster's soul in the first place. His compassion, his kindness, his hope for better things arose and took their place, and he eased himself of tension he never realized he had held onto so desperately. It felt good to let go, to let himself drop the guards and walls he had established over the years. He felt so much more free. 

When he finally looked back up at Sara there were tears spilling from his eyes. But it wasn't the sight of them, nor the touch of his hands wrapping around her wrists, that made her startle. Rather, it was the color of his eyes. The dark red that originally made them that intimidating wine color was no longer there, leaving behind a soft, gentle shade of lavender purple. Sara felt the corners of her mouth pull up ever so slightly at the sight of it. If that was the true color of who he was, of his magic, then she much preferred it to the other. 

She startled again when Gaster slid out of the chair and came down to his knees, bringing her down with him. His long arms wrapped around her and she brought herself down to her knees, now having to look up at him while he hunched over her. He was whispering her name over and over again in a tone similar to what one would use when repeating 'thank you' again and again. Sara breathed a sigh as she brought her own arms around him, her peace mingling with his.


	8. Changed for Good

She didn't realize she had fallen asleep until she was waking up. Blinking, she looked around despite her bleary eyes. She expected to be back in her room next to Chloe as it had already become a habit for her, but instead she was tucked into a large futon style bed that had the minimum when it came to bedding and sheets. There wasn't even a pillow, but the girl seemed to have slept well enough regardless. She rubbed her eyes and then got herself to sit up, looking around again and finding Doctor Gaster seated with his back to her. He looked to be going through all his previous notes what with the amount of papers completely obscuring the surface of his desk. 

A moment after her eyes landed on him he shifted, straightening a little, and swiveled his chair around to look at her due to his having sensed the slight shift in her soul. It still surprised her to look into his eyes and see lavender purple instead of the wine color she had gotten used to. His whole demeanor was less tense, and even the feeling around him was far more gentle than before. She felt his mood lift as his own gaze met hers and she couldn't help but give him a smile for the first time. 

"You...you slept well, I hope?" he asked. His tone was softer, smoother. It was so different from the tone had before with its usual hissing and growling. There was no need for him to sound threatening or dangerous anymore. Though, there was a bit of a rasp to his voice due to his having spoken so harshly for so long. 

"Yes. Did you sleep at all?" she asked back.

"A little. I've been distracted," he replied as he looked back towards his desk and the papers scattered everywhere on its surface. "I must change how things work here. I cannot continue to treat you, or any human here, as some _thing_ for me to use as I please. You're more than that. You're individuals." He turned his head again to look towards Sara once more. "Just as you are not S4-R4, you're Sara."

It was an absentminded gesture at this point but Sara brought a single hand up to touch the collar around her neck. But it wasn't there. With a confused expression she traced her hands around her neck to confirm that the collar was, indeed, missing. It had remained around her neck for so long she'd since gotten used to the feel of it, so it was a curious sensation to realize that it was gone. 

"I removed it while you slept," Gaster said as he watched her. 

She didn't really know why she did it but her eyes searched the room for a sign of where he might have taken the collar. Perhaps it was her curiosity, or a need to be sure that it really was no longer a part of her. She found it sitting on his desk peeking out from under a leaf of paper. It looked like it had simply been tossed aside-- _discarded_. After all the previous times of Gaster being the one to break down it was Sara's turn to start crying. She stared at him in disbelief, as well as overwhelming gratitude, as she continued to realize that he didn't consider her a slave, a possession or an object, but as who she was. 

Her emotions within Gaster made it feel like his soul was twisting, and he rose from where he sat to close the distance between them before he quietly sat down on the edge of the bed close to her. Without a word he reached out and gently stroked away the tears that had already wet her cheeks. She could feel his concern for her so she didn't flinch or shy away at his touch, but instead leaned into it. 

"Thank you," she whispered.

"It is I who should be thanking you," he replied. "It was...unexpected...how all this happened, but you've helped me remember who I used to be, how I used to be."

"So, what now?"

"I will help you continue to recover from what I've put you through. I will seek forgiveness from the others that I've hurt. And, I will help my aides remember how they used to be as well."

"But..."

"I must be hopeful, like you," he said before she could even try to voice her concerns or doubts. "I know it won't be easy, Sara. It wasn't easy what you had to go through to get to me, but you did. You managed to bring back the parts of me that I had put away, even lost." Gaster tilted his head down as if to touch his forehead to hers, but he kept himself a breath's distance from her, and simply looked down at her with a gentle expression. "I will never be able to repay you for that."

"I don't expect you to," she replied. "I just wanted the pain to go away, the fact that it was yours made it that much more surprising."

"Still...I thank you." 

Finally he closed the space between them and the two closed their eyes, taking in the moment, as their foreheads rested against each other's. Sara could feel the rising happiness within Gaster, while he enjoyed the peace and quiet of her soul working within his. All the while Gaster continued to touch and stroke Sara's cheeks, even though he had wiped away all the tears from them moments ago. The two remained that way for some time before Sara stilled his motions by leaning her cheek into his hand and gently grasping it. 

"I'll help you," she said, bringing her eyes up to look up at him. "I'll help the others see that you've changed. And that monsters can change, just like we can."

"You don't have to."

"I want to. That way, neither of us will have be alone in doing one thing or the other."

Admittedly, part of him wanted that. And although he never had to stay it out loud he could feel her soul stirring in him, sensing it. Though she was only a small distance away from him it felt like her arms were wrapped around him, her warmth and gentleness seeping into his bones. He felt better knowing that she was willing to stand with him, and he felt it in himself to do the same for her in her hopes of convincing the other humans. With the same soft expression on his face he returned her smile. 

"No. We won't."

This time Sara did reach out and embrace him. Her hands pressed a little into his spine and ribs while his own hands carefully wrapped behind her back and curved around her shoulders. Gaster took immense comfort in her touch and the sensation of her soul, being the force to help still any lingering doubts or worries he had. Like he had said, it would not be easy to help the others see that kindness, compassion, and understanding could be achieved between humans and monsters, but the end result would be worth it, just like how it was between himself and Sara. 

They would be the start.

**Notes for the Chapter:**

> Thank you, everyone, for reading this silly little story idea I had! I'm grateful for all the comments, kudos, and other bits of encouragement as I was writing this. I hope you enjoyed it. And, I hope y'all continue to enjoy the stories I write.

**Author's Note:**

> Check out my [ TUMBLR ](http://jarofmayonnaise.tumblr.com/) to see what nonsense I like and reblog! Or, feel free to leave me a message~
> 
> 'till next time~


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